Polyether polyol production of a flexible urethane foam and shaped article therefrom

ABSTRACT

A polyether polyol produced by using an N-aminoethylpiperazine-ethylene oxide aduct as an initiator and addition-polymerizing an alkylene oxide thereto and having a molecular weight of about 2000 to 7000; a process for producing a flexible urethane foam starting with the above polyether polyol; a process suited for the production of a hot-cure urethane foam which comprises using the above polyether polyol with a hydroxyl value of 40 to 80 mg KOH/g and, as a blowing agent, 4.6 to 6.0 weight parts of water based on 100 weight parts of the polyol; and a process suited for the production of a cold-cure urethane foam which comprises using the above polyether polyol with a hydroxyl value of 23 to 50 mg KOH/g and, as a blowing agent, 2.5 to 5.0 weight parts of water on the same basis. 
     The use of the polyether polyol enables the production of a low-density, low-hardness flexible urethane foam using a small amount of water, without requiring any environment-unfriendly chlorofluorocarbon and without being accompanied by deterioration of humid age compression set and other characteristics.

FIELD OF THE INVENTION

The present invention relates to a novel polyether and a method forproducing a flexiable urethane foam starting therewith. The inventionspecifically provides a method suited for the production of alow-density, low-hardness flexible urethane foam by the hot cure moldprocess (hereinafter referred to briefly as hot cure process) and amethod for the production of a high-resilience urethane foam by the coldcure mold process (hereinafter referred to briefly as cold cureprocess).

BACKGROUND OF THE INVENTION

Taking advantage of their excellent resiliency, flexible urethane foamshave been used as cushioning and back-rest materials in a broad range ofapplications, such as furniture, bedding, car upholstery and so on.According to the production processes used, such urethane foams areroughly divided into slab foams and mold foams.

A slab foam is available in the shape of a block produced by foamingunder no restraint and pieces of the desired shape are cut out from theblock for use. A mold foam is a shaped article produced by foaming in ametal or plastic mold. Mold foams are mostly used as automotive parts.

The production technology for such flexible urethane mold foams isgenerally divided into the cold cure process and the hot cure process.Both processes have their own advantages and disadvantages. Thus, themold foam produced by the cold cure process is generally known as HR(high resilience) foam and features a high resilience and a large SAGcoefficient, for instance, thus being very desirable in physicalcharacteristics. Moreover, this foam can be cured at low temperature ina short cure time as an additional advantage. It is further advantageousin that the foam yield is high and that the foam hardly cracks orshrinks. However, the applications of the foam produced by this processare limited to high-density cushions because reducing the foam densityresults in drastic aggravation of the humid age compression set.

On the other hand, the hot cure process is disadvantageous in that itrequires not only a high curing temperature but also a long cure timeand due to a variation in the amount of the catalyst and fluctuations ofmold temperature and depending on mold geometry, defects such as cracks,shrinkage and loose skin are liable to develop in the product foam.Moreover, the product yield is also poor. However, the hot cure processis superior to the cold cure process in that the former enables theproduction of a low-density foam improved in compression set. Therefore,among the flexible urethane foams produced by the hot cure method,low-density foams are generally used as back-rest materials and medium-to high-density foams as cushioning materials.

Thus, the density and hardness of flexible urethane foams should becontrolled according to intented applications.

It is common practice to use CFC-11 (trichlorofluorocarbon), which is acontrolled chlorofluorocarbon, for inhibiting scorching and avoiding therisk of a fire or for implementing a low degree of hardness in theproduction of slab foams with a density of not more than 22 kg/cm³ orfor controlling the hardness (realizing a low hardness value) and forimplementing a low foam density in the production of foams by the hotcure process for use as automotive seat back-rest materials.

However, the recent control over the use of chlorofluorocarbons for theprotection of the ozone layer is expected to become more and morestringent and ultimately lead to a complete ban on their use. In view ofthe imminent complete ban, the development of a technology for producinga low-density, low-hardness urethane foam without employing achlorofluorocarbon is an urgent task to be tackled. The approaches sofar made to this end generally comprise a switchover from CFC-11 to CH₂Cl₂ and the use of an increased amount of water in the formulation. Onthe other hand, as to mold foams, the polyol is modified and the amountof water in the batch formula is increased to reduce chlorofluorocarbonrequirements. Regarding the hot cure process, technologies for producinga low-density, low-hardness urethane foam which comprise using wateralone as the blowing agent and increasing the pouring temperature beyondthe conventional level have been disclosed in Japanese Tokkyo Kokai KohoH-3-176110, H-3-192109, H-2-11614 and H-3-3689, among others. However,unlike the case using a chlorofluorocarbon, it is difficult to produce alow-hardness flexible foam having satisfactory physical characteristicsby using water alone as the blowing agent. To overcome this difficulty,a method employing a monool or diol-based polyoxyalkylene polyol as partof the polyol component has been proposed but this method has thedrawback that the humid age compression set is increased and otherphysical properties are also sacrificed.

However, increasing the amount of water in the formulation causes anincreased evolution of carbon dioxide gas according to the reaction--NCO+H₂ O→˜NH₂ +CO₂ and although the CO₂ gas contributes to foaming, ofcourse, it encourages the crosslinking reaction as follows. ##STR1##This crosslinking reaction and hydrogen bonding between the resultingurea bonds unavoidably increase the hardness of the product foam.Therefore, when a urethane foam of a given density is produced byincreasing the amount of water instead of using CFC-11, a substantialincrease occurs in the hardness of the foam. Furthermore, the use ofwater in an increased quantity adversely affects physical propertiesincluding compression set in a considerable measure. Modifying thepolyol may result in some improvement in compression set but be scarcelyeffective in controlling the increase of hardness.

When the urethane foam is intended for use as the back rest of a carseat, such an increased hardness is definitely unacceptable. Since areduction in chlorofluorocarbon consumption is an urgent requirementtoday, a certain increase in hardness is tolerated today but the demandfor reduced hardness is persistent.

It is true that the following methods for reducing the hardness of foamshave been known for years. One of the methods comprises lowering the NCOindex (isocyanate indicator) [the equivalent number of isocyanate groupsper 100 active hydrogen atoms; --NCO and --OH/H₂ O are in the ratio of1:1 at the NCO index number of 100] of the reaction system and the othercomprises adding a monohydric or dihydric alcohol to lower thefunctionality of the polyol component.

However, these known methods have major disadvantages such as poormoldability, undercure and poor physical characteristics of the foam(particularly humid age compression set).

On the other hand, by virtue of their satisfactory physical properties,HR foams are meeting an increasing portion of the demand but itsgreatest drawback is that this kind of foam cannot be easily reduced indensity as compared with the hot cure mold foam.

It is, therefore, a further object of the present invention to provide aprocess for producing an HR foam of low density and low hardness withoutsacrificing the physical properties, particularly humid age compressionset, of the foam and with acceptable moldability.

Among the HR formulation recently proposed, there is the formula called"all-MDI formula" employing some special MDI.

This type of formula offers a number of advantages such as high curerate, high durability, ease of varying hardness, etc. and the demand forthe foams produced from this type of formula is increasing.

However, this type of formula is hardly conducive to hardness reductionin the absence of CFC-11 and, in the domestic market, is claiming only alimited segment of the market, typically the head rest market, wherefoams of comparatively high density are still acceptable.

The all-MDI foam cannot be reduced in density to the extent that can beobtained with TDI-80 and TM-20 (TDI-80/polymeric MDI=80/20) but is alsorequired to be supplied in the low density range.

On a laboratory scale, it is not impossible to produce a low-density HRfoam by no more than increasing the amount of blowing agent water.However, the humid age compression set characteristic of the foamdeteriorates drastically in proportion to the increasing amount of H₂ O,with an associated aggravation of foam moldability. In other words, sucha system is not suited for the production of foams of intricate design.

The object of the present invention is to solve the above-mentionedproblems associated with the production of low-density, low-hardnessflexible urethane foams.

More particularly, the object of the invention is to provide a processfor producing a low-density, low-hardness flexible urethane foam withoutemploying a controlled chlorofluorocarbon and, instead, using watersubstantially alone as a blowing agent. The further primary object ofthe invention is to create a novel polyether polyol for theestablishment of an environment-friendly production technology andprovide a novel process for producing a flexible urethane foam startingwith such a specially created polyether polyol as part of the polyolcomponent, which process does not necessarily require the use of achlorofluorocarbon.

SUMMARY OF THE INVENTION

The inventors of the present invention found, after a great deal ofresearch endeavor to improve the starting material polyether polyol,which is known to have a profound influence on the moldability andphysical properties, in particular, of a flexible urethane foam, that apolyether polyol having a specific structure, shown below, acts in aunique way in the production system for a urethane foam which employswater as a principal blowing agent. This finding was followed by furtherresearch, which has culminated in the development of the presentinvention.

It is, therefore, an object of the invention to provide a polyetherpolyol produced by addition-polymerizing an alkylene oxide to anN-aminoethylpiperazine-ethylene oxide adduct as a polymerizationinitiator and having a molecular weight of 2000 to 7000.

It is another object of the invention to provide a process for producinga flexible urethane foam characterized by reacting a polyol comprisingthe polyether polyol with an organic polyisocyanate in the presence of asurfactant and a blowing agent.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows the relationship between density and hardness for the HRfoams obtained in Examples 6 and 7 and Comparative Example 9.

In FIG. 1. denotes the foam of Example 6, the foam of Example 7, and xthe foam of comparative Example 9.

DETAILED DESCRIPTION OF THE INVENTION

The N-aminoethylpiperazine-ethylene oxide adduct, prior to the additionpolymerization of alkylene oxide, includes the structure of thefollowing formula (hereinafter referred to as APE structure). ##STR2##

The alkylene oxide (oxyalkylene unit; hereinafter referred to asalkylene oxide) to be addition-polymerized is preferably ethylene oxide(oxyethylene) and/or propylene oxide (oxypropylene). In this connection,ethylene oxide and propylene oxide units may occur in a randomarrangement or in blocks. ##STR3## wherein W, X and Y independently mean##STR4## wherein R¹ and R² independently represent H or CH₃ ; m and nare 35≦m+n≦150; the number being that which is necessary to satisfy themolecular weight condition of 2000-7000.

The polyether polyol of the invention may be any polyether polyol havingthe above APE structure and may also be a polymer polyol based on apolyether polyol having this structure.

The polyether polyol of the invention (hereinafter referred to sometimesas APE polyol) preferably has a molecular weight of not less than 2000.With an APE polyol having a molecular weight of less than 2000, it isdifficult to provide a flexible urethane foam. Generally, an APEpolyether polyol with a molecular weight not exceeding 7000 is employed.Regarding the remainder of the polyol structure, the preferred polyolhas ##STR5## (oxyethylene group; hereinafter referred to sometimes asethylene oxide or EO) and ##STR6## (oxypropylene group; hereinafterreferred to sometimes as propylene oxide or PO). The EO and PO may occurin any desired combination. Thus, the combination may be random, forinstance. The proportion of oxyethylene (ethylene oxide) units ispreferably not more than 20%. If the proportion of oxyethylene be toogreat, it would be difficult to produce a foam or, for that matter, asatisfactory flexible foam.

The oxyethylene units at the terminals of the polyol molecule are usefulfor the formation of terminal primary --OH radicals but the availabilityof too many --OH radicals tends to yield a closed-cell foam, instead ofgiving a satisfactory flexible foam. Therefore, the oxyethylene unitsdirectly bound to the terminal hydrogen atoms preferably account for notmore than 15% in the polyol molecular weight range of more than 4000 andnot more than 10% in the polyol molecular weight range of 2000 to 4000.

A polyether polyol having the above-mentioned structure can besynthesized by the known processes or any process analogous thereto.Generally, the following routes of synthesis can be utilized. ##STR7##(aminoethylpiperazine) is heated in a N₂ stream and at least 2 molarequivalents of ethylene oxide (OE) are added to give ##STR8## [referredto as APE-H structure; the APE structure mentioned earlier correspondsto this APE-H structure after elimination of hydrogen atoms).

When the amount of EO so added is 3 molar equivalents or greater,stoichiometrically the whole polyether has APE-H and APE structures buteven when the amount is at least 2 molar equivalents, APE-H is includedin the reaction product.

To the APE-H or APE-H-containing reaction mixture thus obtained is addedKOH and the mixture is dehydrated. This operation is performed to causethe reaction KOH+˜OH˜OK+H₂ O.

This operation is also intended to inhibit formation of the followingbyproduct diol from the KOH catalyst. ##STR9## Depending on uses for thepolyol, the presence of the byproduct diol may be tolerated.

The dehydration can be performed generally by heating the system to 100°to 130° C. and bubbling an inert gas such as N₂ through the system , byheating the system under reduced pressure or by azeotropic distillationwith toluene. The proper amount of KOH is 0.1 to 0.4% based on the finalreaction product. As the catalyst, NaOH or the like can be used in lieuof KOH.

Then, EO (ethylene oxide) or PO (propylene oxide) is added and reactedat a temperature in the neighborhood of 100° to 120° C. The amount of EOand/or PO so added should of course be selected according to the desiredmolecular weight of the final product.

After addition of PO or EO in the amount corresponding to the desiredmolecular weight (hydroxyl value), the catalyst KOH is inactivated byaddition of an acid such as diluted hydrochloric acid, dilute sulfuricacid or phosphoric acid or an alkaline adsorbent such as syntheticmagnesium silicate or by addition of both. The reaction mixture is thenfiltered to remove insolubles and the excess water is removed bydecompression or bubbling an inert gas. Generally, this dehydration iscarried out until a water content of not more than 0.05% is attained.For the ease of maintaining the stability of the product polyetherpolyol, it is common practice to add at least about 500 to 1000 ppm ofBHT (2,6-di-tert-butyl-4-methylphenol).

The above procedure provides a polyether polyol of the presentinvention.

In the production of a flexible urethane foam according to theinvention, a filled polyol (a so-called polymer polyol) obtainable bypolymerizing an ethylenically unsaturated monomer such as styrene and/oracrylonitrile in the presence of a radical polymerization initiator inthe above polyether polyol can be employed. The resulting polymer of themonomer is partially grafted to the polyether chain at times but ismostly dispersed in a stable condition in the polyether polyol.

The polyether polyol of the invention, thus produced, can then be usedin the production of a flexible urethane foam.

The production of a flexible urethane foam starting with the polyetherpolyol of the invention can be carried out in the Der se conventionalmanner.

The polyol comprising the polyether polyol of the invention is reactedwith an organic polyisocyanate in the presence of a surfactant and ablowing agent, with or without addition of a catalyst, flame retardant,stabilizer, colorant, etc., to synthesize a flexible urethane foam.

As the polyol, the APE polyether polyol of the invention can be usedalone or in admixture with a commercial polyether polyol. Inconsideration of the ease of handling, the use of a blend with acommercial polyol is preferred. The hydroxyl value of the blend polyolis preferably about 20 to 80 mg KOH/g. As to the catalyst, surfactant,etc., commercial products can be employed.

As the blowing agent, H₂ O is primarily employed but a low-boilingorganic substance such as CH₂ Cl₂, CFC-11 or HCFC-141b can beadditionally employed. The organic polyisocyanate which can be usedincludes tolylene diisocyanate (TDI), diphenylmethane diisocyanate(MDI), modified MDI, polyphenylpolymethylene polyisocyanate (polymericMDI), etc. as well as mixtures thereof.

The proportion of the organic polyisocyanate is generally about 0.8 to1.5 equivalents based on the OH of the polyol and H₂ O.

The polyether polyol can be used in the production of whichever of aslab foam and a mold foam.

The further object of the invention is to provide a process forproducing a flexible urethane foam starting with the above APE polyetherpolyol of the invention.

The present invention is, therefore, directed to a process for producinga flexible urethane foam characterized by reacting a polyether polyolprepared.

The process is particularly suited for the production of a hot cureflexible urethane foam of low density and low hardness, comprises (i)using an aminoethylpiperazine-ethylene oxide adduct of theabove-mentioned APE structure as the initiator and addition-polymerizingan alkylene oxide thereto and having a hydroxyl value of 40 to 80 mgKOH/g as part of the polyol component and (ii) reacting it with anorganic polyisocyanate the presence of 4.0 to 6.0 parts by weight ofwater based on 100 parts by weight of the polyol component.

As mentioned above, a flexible urethane foam is generally manufacturedusing the polyol, organic polyisocyanate, cell size regulator, blowingagent and, optionally, catalyst, flame retardant, color and otheradditives.

While this process of the invention is characterized in that a polyetherpolyol of the above-described APE structure is employed, the ethyleneoxide content of the polyether polyol to be used is preferably not morethan 20%. If the EO content is too large, it becomes difficult toprovide a satisfactory open-cell foam. The ethylene oxide units added tothe terminals of the molecule preferably account for not more than 10%based on the total polyol.

This is because the use of EO in excess tends to cause a closed-cellstructure.

The whole amount of the polyol may be provided by the polyether polyolof the invention. However, since the reaction then proceeds veryrapidly, the use of a commensurate reaction vessel is recommended. Whena conventional reactor is employed, it is preferable to use a blend ofnot more than 40% of the APE polyether polyol and the balance of otherpolyol or polyols. However, if the proportion of the APE polyetherpolyol is less than 5%, the effects of the invention will not be fullymaterialized.

The other polyol which can be used in combination may be any knownpolyol having a hydroxyl value of 40 to 80 mg KOH/g and the use of acommercial polyol for hot cure use leads to better results. For example,Actcol MF-26, MF-53 and MF-67, all available from Takeda ChemicalIndustries, Ltd., can be mentioned.

The hydroxyl value of the blend polyol is preferably about 45 to 75 mgKOH/g, and the proportion of terminal primary OH groups is preferably55% or less and, for still better results, 30% or more.

If the hydroxyl value is too large, foam stability is sacrificed to makeit difficult to provide a satisfactory foam. Conversely, if the OH valueis too small, the physical properties, particularly humid agecompression set, of the foam are adversely affected.

On the other hand, too large a proportion of terminal primary OH groupstends to encourage the formation of a closed-cell foam. Conversely, ifthe proportion is too small, curability is sacrificed, although a foamis obtained at any rate. However, in consideration of productivity, theproportion of terminal primary OH groups is preferably 30% or more.

The organic polyisocyanate to be used in the process of the invention ispreferably tolylene diisocyanate (hereinafter referred to as TDI) andmore preferably TDI-80 (Takenate 80:2,4-TDI/2,6-TDI=80/20; TakedaChemical Industries).

In the process of the invention, the above-described polyol and organicpolyisocyanate are used in the isocyanate index range of 80 to 120. Ifthe isocyanate index value is less than 80, the physical properties suchas humid age compression set of the foam tends to be sacrificed. On theother hand, when the isocyanate index exceeds 120, curability issacrificed and the hardness of the foam is also compromised.

In this process of the invention, water alone is used as the blowingagent. The amount of water should be in the range of 4 to 6 parts byweight based on 100 parts by weight of the polyol used. If the amount ofwater is less than 4 parts by weight, the foam density is increased sothat the objective low-density foam cannot be obtained. However, if morethan 6 parts by weight of water is employed, the objective low-hardnessflexible foam cannot be obtained.

An amine catalyst is not essential to the process of the invention butcan be used in the amount generally employed. The amine catalyst may forexample be triethylenediamine (TEDA), pentamethyldiethylenetriamine,N-ethylmorpholine or the like. Preferably, a tin catalyst such asstannous octoate is used concomitantly.

It should be understood that the catalyst which can be used in thepractice of the invention is not limited to the species mentioned above.

The surfactant which can be used may be any of the surfactants for slabfoams and those for hot cure mold foams. Among such surfactants areB-8017, B-2370 (both available from Goldschmidt), L-582, L-5740M,L--5740 S (all available from Nippon Unicar), SH-190 and SRX-293 (bothavailable from Toray Silicone). Such surfactant is generally used in aproportion of 0.5 to 2 parts by weight based on 100 parts by weight ofthe polyol.

Furthermore, depending on the required characteristics of the productflexible foam, a flame retardant such as tris(2,3-dichloropropyl)phosphate, halogen-containing condensed organic phosphoric esters (e.g.CR 505 available from Daihachi Chemical Industries) etc., colorant,antioxidant, viscosity reducing agent such as propylene carbonate, andother known additives that may be suitable can also be added.

In the production of a flexible urethane foam by this hot cure process,curing is carried out at a temperature over 100° C. and preferablywithin the range of 100° C. to 200° C.

The process also, particularly suited for the production of an HR foam,comprises (i) using a polyol comprising an APE polyether polyol preparedby using an aminoethylpiperazine-ethylene oxide adduct as an initiatorand addition-polymerizing an alkylene oxide thereto and said polyetherpolyol having a hydroxyl value of 23 to 50 mg KOH/g and (ii) water as ablowing agent in a proportion of 2.5 to 5.0 parts by weight to each 100parts by weight of the polyol to provide a high-resilience urethanefoam.

The polyol which can be used in this process of the invention ispreferably an APE polyether polyol with a hydroxyl value of 23 to 50 mgKOH/g. If the hydroxyl value exceeds 50, the foaming reaction tends togive a closed-cell structure so that a satisfactory HR foam cannot beobtained.

On the other hand, an APE polyether polyol with a hydroxyl value of lessthan 23 cannot be easily produced by the usual production procedure.

The amount of said APE polyether polyol is preferably not less than 30%.If the amount of said APE polyol is less than 30%, no sufficient effectwill be realized.

In the process of the invention, the above APE polyol can be used incombination with a commercial polyol. Any commercial polyol can be usedfor this purpose but it is preferable to see to it that the hydroxylvalue of the polyol blend will be in the range of 23 to 45 mg KOH/g. Apolyol blend with a hydroxyl value of less than 23 is hardly available,while the use of a polyol blend with a hydroxyl value of more than 45does not provide a satisfactory foam.

The polyol which can be advantageously used concomitantly includes,inter alia., Actcol GE-3412 (OH value 34, viscosity 950 mPa.s) , MF-81(35 and 1100 respectively), MF-83 (35 and 950, respectively), MF-85 (28and 1400, respectively), POP-28 (polymer polyol, OH value 28, viscosity2800) and POP-18 (polymer polyol, OH value 30, viscosity 2000).

The APE polyol is preferably a polyol prepared by addition-polymerizingpropylene oxide and/or ethylene oxide, with ethylene oxide accountingfor 5 to 25%. Among them, one having a terminal ethylene oxide contentof 5 to 20% is preferred. If the ethylene oxide content is too large, anopen-cell HR foam having a satisfactory cushioning property can hardlybe obtained. Conversely, when the EO content is too low, a satisfactoryfoam may not be obtained.

The amount of water for use as a blowing agent in accordance with theinvention is 2.5 to 5.0 parts by weight. If the amount of water is lessthan 2.5 parts by weight, a low density foam cannot be obtained in anyevent and, therefore, it is futile to employ the specified polyol. Ifthe amount of water is more than 5.0 parts by weight, the foam densitywill become too low and no adequate physical characteristics berealized.

While water can be a sole blowing agent, the use of a low-boilingorganic substance such as CFC-11, HCFC-141b or the like as an auxiliaryblowing agent is permissible.

The surfactant for use in the above production process of the inventionmay be any foam stabilizer for HR foams. Among such surfactants areB-4113, B-4690, B-8650 (all available from Goldschmidt), L-5305, L-3600,SZ-1313 (all available from Nippon Unicar), SRX-274C, SF-2962 (bothavailable from Toray-Dow Corning) and so on. The amount of such cellsize regulator is generally 0.5 to 2 parts by weight based on 100 partsby weight of the polyol.

The catalyst which can be used in this process of the invention may beany of those available commercially for the production of urethanefoams. Thus, for example, tertiary amines such as triethylenediamine(TEDA) and tetramethylhexanediamine (TMHDA) can be mentioned. However,if a sufficient reaction rate can be achieved, such a catalyst need notbe employed.

A crosslinking agent is sometimes used in the production of HR foams.The crosslinking agent includes, among others, low molecular compoundssuch as ethylene glycol, glyerine, etc., aminoalcohols such asmonoethanolamine, diethanolamine, etc., and polyether polyols having ahydroxyl value of not less than 400, e.g. an ethylenediamine-PO adduct.

If necessary, a flame retardant, a colorant and other additives can beadded.

The organic polyisocyanate for use in this process includes, amongothers, tolylene diisocyanate (hereinafter referred to as TDI), 2,4'and/or 4,4'-diphenylmethane diisocyanate (MDI), their modificationproducts, their prepolymers with polyols, polyphenylpolymethylenepolyisocyanate (hereinafter referred to as polymeric MDI), and mixturesof such polyisocyanates.

In this process of the invention, too, said polyol, H₂ O and organicpolyisocyanate are used in a formulation giving an isocyanate index(hereinafter referred to as NCO index) of 80 to 120. If the isocyanateindex is less than 80, the physical properties, such as humid agecompression set, of the foam tend to be sacrificed. Conversely if theisocyanate index exceeds 120, scorching tends to occur and the foam willbe unsatisfactory in hardness and other parameters.

In the above process, the materials other than the organic isocyanateare premixed beforehand and this premix is admixed with the isocyanatein a high-speed mixer for several seconds. For production on acommercial scale, it is advantageous to use a foaming machine formixing.

For the production of an HR foam by the cold cure process, curing iscarried out preferably at a temperature between 30° and 80° C. and morepreferably between 50° and 70° C.

The present invention provides the following effects. Thus, with thepolyol of the invention (inclusive of its use as part of the polyolcomponent), the following remarkable effects are obtained.

(1) The 25% ILD (compressive hardness JIS-K6401) value can be decreased,by 2 kg or more, without affecting the compression set.

(2) In the production of the so-called mold foam, the water requirementscan be decreased. Thus, when the foaming reaction is carried out withthe same amount of water, the use of the polyol of the inventionprovides for a foam of lower density. Thus, the foaming efficiency isconsiderably improved.

(3) The amount of the amine catalyst which is used in the production offoams can be reduced or even the catalyst can be substantially dispensedwith. While an amine catalyst is generally required for the productionof foams, it is well known that the residual amine catalyst in foams canbe a cause of discloration and degradation. In this respect, too, thepolyol of the invention has a unique advantage.

The foam produced by the process of the invention has the followingcharacteristics.

(1) Environment-unfriendly chlorofluorocarbons such as CFC-11 need notbe employed.

(2) The hardness of product foams can be decreased without affectingtheir other physical properties (particularly humid age compressionset).

(3) In the production of foams, the water requirements can be decreased.Therefore, foams can be provided at a reduced cost and the problems (infeeling, hardness, permanent strain, etc.) associated with the use ofwater in a large amount can be eliminated.

EXAMPLES

The following examples, comparative examples and reference examples areintended to describe the present invention in further detail and shouldby no means be interpreted as defining the scope of the invention.

EXAMPLE 1

A reactor equipped with heater and stirrer means is charged with 2.7 kg(20.9 moles) of aminoethylpiperazine and the internal atmosphere isreplaced with N₂ gas. The charge is heated to 120° C. and 2.76 kg (62.7moles) of ethylene oxide is added for addition polymerization. Thisreaction provides an aminoethylpiperazine-3EO adduct (the structure ofthe invention).

Then, 150 g of KOH flakes are added and N₂ gas is bubbled through thereaction mixture. After dehydration to a water content of not more than0.1%, 57.0 kg of propylene oxide is introduced at 105°-115° C. and,then, 3.3 kg (5% in the polyol) of ethylene oxide is introduced forfurther reaction.

After completion of the reaction, a small quantity of water andsynthetic magnesium silicate (KYOWAAD 600, the trademark of KyowaChemical Co.) are added for adsorption of potassium hydroxide. Themixture is then filtered to remove insolubles, followed by dehydrationto a moisture content of not more than 0.05%. Then, 65 g of BHT(2,6-di-tert-butyl-4-methylphenol (available from YoshitomiPharmaceutical) is added.

The polyol A thus synthesized has a hydroxyl value of 63.5 mg KOH/g anda viscosity of 610 mPa.s (25° C.). This polyol contains 5% ofoxyethylene and 8.3% of APE (% by weight).

EXAMPLE 2

The same reactor as the one used in Example 1 is charged with 2.72 kg ofan aminoethylpiperazine-3EO adduct separately synthesized and 150 g ofKOH flakes are added.

Thereafter, 52.3 kg of propylene oxide is introduced for additionpolymerization and, then, 7.5 kg of ethylene oxide was furtherintroduced. The reaction mixture is neutralized and purified as inExample 1, followed by addition of 63 g of BHT to provide a polyol B.

This polyol B has a hydroxyl value of 35.8 mg KOH/g, a viscosity of 930mPa.s (25° C.), an oxyethylene content of 12% and an AEP structurecontent of 4.3%.

EXAMPLE 3

A 5-liter autoclave is charged with 750 g of polyol B and after repeatednitrogen purging, a premix of 3250 g of polyol B, 500 g ofacrylonitrile, 500 g of styrene monomer and 30 g of AIBN is introducedat 120° C. with constant stirring over 3 hours. The unreacted monomersare removed under reduced pressure to provide a polymer polyol. Thispolymer polyol has an OH value of 27.5 mg KOH/g and a viscosity of 2440mPa.s (25° C.) (polyol C).

COMPARATIVE EXAMPLE 1

Using the same reactor as the one employed in Example 1 and by the sameprocedure as Example 1, polyol D is synthesized. Thus, 3.76 kg (64.5moles) of propylene oxide is added to 2.77 kg (21.5 moles) ofaminoethylpiperazine and after addition of 150 g of KOH flakes anddehydration, 0.58 kg (10 moles) of propylene oxide is added. By thisaddition of PO, an oxypropylene unit is added to every --NH group of theaminoethylpiperazine and, therefore, no APE structure is present in thispolyol. (Therefore, this polyol is not the polyol of the invention).

Thereafter, 1.89 kg of ethylene oxide is added and, then, 51.0 kg ofpropylene oxide is added, followed by further addition of 3.2 kg ofethylene oxide (5.1% terminal oxyethylene content). The reaction mixtureis treated with synthetic magnesium silicate to adsorb KOH and filtered.Then, 63 g of BHT is added.

The resulting polyol D has a hydroxyl value of 62.4 mg KOH/g and aviscosity of 560 mPa.s (25° C).

This polyol has an APE content of 0 and an oxyethylene content of 8.1%,which includes a terminal EO content of 5.1%.

COMPARATIVE EXAMPLE 2

A reactor is charged with 3.17 kg of triethanolamine and 150 g of KOHflakes and, then, 2.7 kg of ethylene oxide is added. After dehydration,52.0 kg of propylene oxide is added. Then, 3 kg of ethylene oxide isfurther added and after neutralization and purification, 61 g of BHT isadded, whereby a polyol E is obtained. This polyol E has a hydroxylvalue of 56.3 mg KOH/g, a viscosity of 480 mPa.s, and an oxyethylenecontent of 9.3% which includes a terminal EO content of 4.9%. Of course,its APE content is 0. Examples 4 and 5, and Comparative Examples 3through 8

Using the formulations shown in Table 1, flexible urethane foams areproduced by the hand mixing method. In the table, Ex. 1, Comp. Ex. 1,etc. mean Example 1, Comparative Example 1, etc. Thus, surfactant,catalyst and other additives are added to 200 g of each polyolbeforehand and stannous octoate is added to the premix. To this isquickly added TDI-80 (Takenate 80, Takeda Chemical Industries) and themixture is agitated on a mixer for 5 seconds. This composition is pouredinto an aluminum mold, 320×320×70 mm, which has been preheated to atemperature of 40°±1° C. After foaming, the product is post-cured in acuring oven at 180° C. for 12 minutes. The physical properties of theproduct foam are shown in Table 1. This process is the so-called hotcure mold process. Among the mold foams according to Example 4 andComparative Examples 3, 4 and 6 in which the same amount of water isemployed, the foam density in Example 4 is remarkably lower. In order toobtain a foam of the same density as that of the foam of Example 4, notless than 5.7 parts of H₂ O is required as in Comparative Example 7.

To achieve the density value of Comparative Example 3 using the polyolof Example 1, the H₂ O requirement is not more than 4.7 parts. Theeffect of the polyol of Example 1 on foam density is remarkable. On theother hand, the hardness values (25% ILD) of the foams according toExamples 4 and 5 are both as low as not more than 10.0 kg.

In a foaming operation by the hand mixing method, it is extremelydifficult to produce a foam with a hardness value of the order of 10 kgwhile insuring a humid age compression set of not more than 15%.However, as demonstrated in Example 3, such a foam can be easilyproduced when the polyol of the invention is employed. Actcol MF-53,which is a commercially available substitute for chlorofluorocarbons,gives a foam with a density of 35.4 kg/m² and a 25% ILD hardness of 13.5kg with the same amount of blowing agent, indicating that the foam ofExample 3 is remarkably superior.

To attain a foam density of about 35 kg/m³, the polyol of Example 1requires no more than about 4.7 parts of H₂ O as demonstrated in Example5 and the 25% ILD value of the foam is less than 10 kg. The effect ofthis Example 2 is also remarkable.

Comparative Examples 4 and 5 employ the polyol of Comparative Example 1.The polyol of Comparative Example 1 is structurally similar to thepolyol of Example 1 but is not a polyol prepared usingaminoethylpiperazine-EO adduct as the initiator.

As apparent from Table 1, there is a marked difference between Example 4and Comparative Example 4.

The foam of Comparative Example 8 is a low-hardness, low-densityflexible foam prepared using CFC-11. Many attempts have so far been madeto attain these physical properties. The properties of the foams ofExamples 4 and 5 are not inferior to those properties.

By the present invention, the object of saving on the consumption ofchlorofluorocarbons in the hot cure process has been thoroughlyaccomplished.

Based on the above results, it is clear that the flexible urethane foamstarting with the polyol of the invention has excellent characteristicsand that the polyol of the invention is of great use.

                                      TABLE 1                                     __________________________________________________________________________                       Comp.                                                                             Comp.                                                                             Com.                                                                              Comp.                                                                              Comp.                                                                             Comp.                                            Ex. 4                                                                             Ex. 5                                                                             Ex. 3                                                                             Ex. 4                                                                             Ex. 5                                                                             Ex. 6                                                                              Ex. 7                                                                             Ex. 8                                 __________________________________________________________________________    Actcol MF-53.sup.(1)                                                                     75  75  100 75  75  75   100 100                                   Polyol of Example 1                                                                      25  25  --  --  --  --   --  --                                    Polyol of Comp. Ex. 1                                                                    --  --  --  25  25  --   --  --                                    Polyol of Comp. Ex. 2                                                                    --  --  --  --  --  25   --  --                                    CR-505.sup.(2)                                                                           10  10  10  10  10  10   10  10                                    H.sub.2 O  5.3 4.7 5.3 5.3 5.0 5.3  5.7 4.5                                   TEDA.sup.(3)                                                                             --  --  0.1 --  --  --   0.1 0.1                                   Stannous octoate                                                                         0.07                                                                              0.07                                                                              0.07                                                                              0.07                                                                              0.08                                                                              0.07 0.07                                                                              0.10                                  L-5740M.sup.(4)                                                                          1.0 1.0 1.0 1.0 1.0 1.0  1.0 1.0                                   Takenate 80                                                                              61.8                                                                              56.0                                                                              62.1                                                                              61.8                                                                              58.9                                                                              61.8 66.0                                                                              52.3                                  Isocyanate index                                                                         100 100 100 100 100 100  100 100                                   CFC-11                                  10                                    [Freerise foaming]                                                            Rise time, min.-sec.                                                                     1-13                                                                              1-16                                                                              1-29                                                                              1-25                                                                              1-30                                                                              2-00 1-18                                                                              1-40                                  Free density kg/m.sup.3                                                                  24.3                                                                              26.5                                                                              24.3                                                                              24.1                                                                              25.3                                                                              24.0 22.3                                                                              22.3                                  Appearance                     No good                                                                       foam                                                                          obtained                                       [Mold foaming]                                                                Overall density kg/m.sup.3                                                               30.4                                                                              34.2                                                                              35.4                                                                              32.4                                                                              34.4                                                                              33.4 32.5                                                                              33.2                                  Actcol MF-53.sup.(1)                                                                     75  75  100 75  75  75   100 100                                   Core density kg/m.sup.3                                                                  26.3                                                                              28.2                                                                              26.8                                                                              26.3                                                                              27.3                                                                              26.6 25.4                                                                              25.5                                  25% ILD kg 314 cm.sup.2                                                                  9.5 10.0                                                                              13.5                                                                              11.4                                                                              11.8                                                                              13.0 12.7                                                                              10.8                                  Ball Rebound (%)                                                                         41  42  38  40  41  40   40  41                                    Air permeability                                                                         70.4                                                                              54.5                                                                              21.8                                                                              48.2                                                                              20.6                                                                              53.8 63.8                                                                              28.3                                  cm.sup.3 /cm.sup.2 · sec                                             Tensile strength                                                                         1.38                                                                              1.30                                                                              1.29                                                                              1.30                                                                              1.21                                                                              1.38 1.53                                                                              1.00                                  kg/cm.sup. 2                                                                  Elongation (%)                                                                           138 133 148 138 130 135  176 144                                   Tear resistance                                                                          0.86                                                                              0.86                                                                              0.95                                                                              0.83                                                                              0.78                                                                              0.86 1.18                                                                              0.69                                  kg/cm                                                                         Compession Set                                                                70° C. × 22 hr (50                                                          10.7                                                                              9.8 13.0                                                                              12.8                                                                              12.7                                                                              13.8 13.4                                                                              9.8                                   compression) %                                                                50° · 95% (humid) ×                                                12.3                                                                              11.4                                                                              16.3                                                                              17.3                                                                              16.8                                                                              17.7 19.3                                                                              15.8                                  22 hr (50%                                                                    compression) %                                                                __________________________________________________________________________     .sup.(1) Manufactured by Takeda Chemical Industries; OH value 70.0 mg         KOH/g, viscosity 450 mPa · s.                                        .sup.(2) Flame retardant manufactured by Daihachi Chemical Industries.        .sup.(3) Catalyst manufactured by Tosoh corp.                                 .sup.(4) Silicone surfactant manufactured by Nippon Unicar.                   Examples 61˜ 63, 71, 72 and Comparative Examples 91˜ 93.     

Table 2 shows a comparison of data generated with various polyols for HRfoams.

Using the various formulations shown in Table 2, HR foams are producedby the hand mixing method. Thus, each polyol, catalyst, surfactant,crosslinking agent and water are admixed to provide a premix. A suitableamount of the premix is taken and formulated with the polyisocyanate soas to give an isocyanate index of 100 (e.g. premix/TM-20=100/43.5 inExamples 6 and 7 and Comparative Example 8) and the mixture is stirredwith a mixer for 5 seconds. The resulting composition is poured into analuminum mold, 400×400×100 mm, which has been heated to 60°-70° C. andcured in situ at the same temperature for 7 minutes. The foam is takenout from the mold and crushed. The sample is allowed to stand for atleast 1 day and its physical properties are determined. Foams of varyingdensity are produced by varying the pouring volume.

The hardness of an HR foam depends on foam density. FIG. 1 shows therelationship between density and 25% ILD. The absence of density plotsless than 37 kg/m³ for Comparative Example 9 indicates that nosufficient density reduction can be achieved with the polyol used inComparative Example 9.

The density- and hardness-reducing effects of the polyol used inExamples 2 and 3 are evident.

These foams also clear the humid age compression set test of ≦20%, witha definite difference from the foams of Comparative Examples.

                                      TABLE 2                                     __________________________________________________________________________               Ex. Ex. Ex. Ex. Ex. Comp.                                                                             Comp.                                                                             Comp.                                             6-1 6-2 6-3 7-1 7-2 Ex. 9-1                                                                           Ex. 9-2                                                                           Ex. 9-3                                __________________________________________________________________________    Formulation                                                                   Polyol of Example 2                                                                      60  60  60  --                                                     Polyol of Example 3                                                                      --          50  50                                                 Actcol · GE-3412.sup.(5)                                                        --          50  50  60  60  60                                     Actcol · POP-18.sup.(6)                                                         40  40  40  --      40  40  40                                     SRX-274C.sup.(7)                                                                         1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0                                    TEDA L-33.sup.(8)                                                                        1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0                                    H.sub.2 O  3.6 3.6 3.6 3.6 3.6 3.6 3.6 3.6                                    Actcol ST-700.sup.(9)                                                                    2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5                                    Diethanolamine                                                                           1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0                                    TM-20.sup.(10)                                                                           47.5                                                                              47.5                                                                              47.5                                                                              47.6                                                                              47.6                                                                              47.5                                                                              47.5                                                                              47.5                                   Isocyanate index                                                                         100 100 100 100 100 100 100 100                                    Physical properties                                                           of molded foam                                                                Overall density kg/m.sup.3                                                               34.4                                                                              36.8                                                                              38.8                                                                              35.6                                                                              37.4                                                                              37.1                                                                              39.4                                                                              41.9                                   Core density kg/m.sup.3                                                                  29.8                                                                              31.2                                                                              37.7                                                                              30.5                                                                              34.7                                                                              31.2                                                                              33.7                                                                              36.3                                   25% ILD kg/314 cm.sup.2                                                                  7.7 8.2 10.2                                                                              8.2 9.7 10.3                                                                              13.3                                                                              15.8                                   Ball rebound %                                                                           56  56  55  58  57  63  65  65                                     Air permeability                                                                         48  30  40  58  53  83  70  60                                     Tensile strength                                                                         1.52                                                                              1.34                                                                              1.39                                                                              1.37                                                                              1.35                                                                              1.06                                                                              1.13                                                                              1.37                                   kg/cm.sup.2                                                                   Elongation %                                                                             110 110 114 111 115 110 101 108                                    Tear resistance                                                                          0.60                                                                              0.63                                                                              0.71                                                                              0.58                                                                              0.63                                                                              0.47                                                                              0.54                                                                              0.58                                   kg/cm                                                                         Compression set                                                               70° C. × 22 hr %                                                            8.3 8.6 8.4 8.5 8.9 7.4 6.8 6.5                                    50° C. · 95% × 22                                                  18.7                                                                              17.4                                                                              17.3                                                                              18.7                                                                              17.5                                                                              30.1                                                                              27.7                                                                              26.0                                   hr %                                                                          __________________________________________________________________________     .sup.(5) Manufactured by Takeda Chemical Industries; trifunctional,           hydroxyl value 35.0 mg KOH/g, viscosity 870 mPa · s.                 .sup.(6) Manufactured by Takeda Chemical Industries; acrylonitrile/styren     polymer polyol, polymer content 20%, hydroxyl value 29.7 mg KOH/g,            viscosity 2,000 mPa · s.                                             .sup.(7) Silicone manufactured by Toray Dow Corning.                          .sup.(8) Catalyst manufactured by Tosoh Corp.                                 .sup.(9) Crosslinking agent manufactured by Takeda Chemical Industries;       hydroxyl value 680 mg KOH/g, viscosity 6,300 mPa · s.                .sup.(10) TDI80/Lupranate M20S.sup.(11) = 80/20 mixture.                      .sup.(11) Polymeric MDI manufactured by BASF.                            

Reference Example 1

A reactor equipped with heater and stirrer means is charged with 18.5 kgof Lupranate MI (MDI, available from BASF) and 34.5 kg of Lupranate M(MDI, BASF) at a temperature of 70°-80° C.

Then, 17.0 kg of Takelac P-21 (a diol with an OH value of 56, availablefrom Takeda Chemical Industries) is added over 1 hour and the charge ismaintained at a temperature of 70°-80° C. for 2-3 hours. Thereafter, 30kg of Lupranate M-20 (polymeric MDI, available from Takeda-BurdischUrethane) is added to provide a modified MDI with an amine equivalent of159.5 and a viscosity of 102 mPa.s (25° C.).

EXAMPLES 8 AND 9, AND COMPARATIVE EXAMPLES 10 AND 11

Table 3 shows examples of all-MDI formulation.

The formulations of Example 8 and Comparative Example 10 aresubstantially identical. Moreover, the two formulations are not muchdifferent in free rise foaming density. However, when mold foams areproduced from these formulations in the same manner as Example 6-1, amarked difference is found in foam density. Of course, the HR foamvaries in density according to the pouring volume but when the pouringvolume of Comparative Example 10 is decreased, the foam does not fill upthe cavity so that a foam with a density of less than 53 kg/m³ cannot beobtained.

A foam of the same density as that of Comparative Example 10 can beprovided, as in Example 9, even at a reduced H₂ O level of 3.0 parts.

The physical properties of the foams are shown in Table 3. The inventionprovides low-density, low-hardness foams with sufficiently low permanentstrain values. The humid-heat permanent strain values of the foams arealso less than 10%.

The above examples also indicate the effectiveness of the process of theinvention.

                  TABLE 3                                                         ______________________________________                                                                    Comp.    Comp.                                                  Ex. 8 Ex. 9   Ex. 10   Ex. 11                                   ______________________________________                                        Polyol of Example 2                                                                           100     100                                                   Actcol MF-15S.sup.(1)           100    100                                    H.sub.2 O       3.5     3.0     3.5    3.5                                    CFC-11          --      --      --     5                                      SZ-1313.sup.(2) 1.0     1.0     1.0    1.0                                    TEDA L-33       0.3     0.3     0.8    0.8                                    CR-4.sup.(3)    3.5     3.5     3.5    3.5                                    Isocyanate C    80.7    71.8    78.7   78.7                                   Index           100     100     100    100                                    (Reactivity)                                                                  CT sec          4       5       8      8                                      RT sec          95      105     119    131                                    Free density kg/m.sup.3                                                                       38.4    43.4    39.8   36.5                                   Physical properties of foam                                                   Overall density 49.8    54.6    54.8   53.3                                   (kg/m.sup.3)                                                                  Core density (kg/m.sup.3)                                                                     44.6    48.7    45.8   45.0                                   25% ILD (kg/314 cm.sup.2)                                                                     13.8    15.4    19.0   19.6                                   Ball rebound (%)                                                                              64      65      59     59                                     Tensile strength                                                                              1.24    1.28    1.23   1.29                                   (kg/cm.sup.2)                                                                 Tear resistance 0.64    0.65    0.61   0.63                                   (kg/cm)                                                                       Elongation (%)  108     107     104    106                                    70° C. × 22 hr                                                                   3.8     3.3     5.4    6.8                                    50° C. 95% × 22 hr (%)                                                           9.8     8.5     13.6   16.5                                   ______________________________________                                          .sup.(1) Triol manufactured by Takeda Chemical Industries, OH value 29 m     KOH/g, viscosity 1,300 mPa · s (25° C.).                      .sup.(2) Surfactant manufactured by Nippon Unicar.                            .sup.(3) Crosslinking agent manufactured by Takeda Chemical Industries, O     value 850 mg KOH/g, viscosity 1,050 mPa · s (25° C.).    

What is claimed is:
 1. A process for producing a flexible urethane foamcharacterized by reacting a polyol comprising the polyether polyolobtained by addition polymerization of an ethylene oxide to anN-aminoethylpiperazineethylene oxide adduct as an initiator, saidpolyether polyol having a molecular weight of about 2000 to 7000 with anorganic polyisocyanate in the presence of a surfactant and a blowingagent.
 2. A process according to claim 1 which is further characterizedby using (i) a polyol comprising the polyether polyol of claim 1 whichhas a hydroxyl value of 40 to 80 mg KOH/g and (ii), as a blowing agent,water in a proportion of 4.0 to 6.0 parts by weight to each 100 parts byweight of said polyol.
 3. A process according to claim 2 wherein thealkylene oxide addition-polymerized for the preparation of saidpolyether polyol is propylene oxide and ethylene oxide, with ethyleneoxide accounting for not more than 20% in all and terminal ethyleneoxide accounting for not more than 10%, both based on the polyol.
 4. Aprocess according to claim 2 wherein the polyether polyol of claim 1 isused in a proportion of 5 to 40% based on the total polyol.
 5. A processaccording to claim 2 wherein said organic polyisocyanate is tolylenediisocyanate.
 6. A process according to claim 1 which is furthercharacterized by using (i) a polyol comprising the polyether polyol ofclaim 1 which has a hydroxyl value of 23 to 50 mg KOH/g and (ii), as ablowing agent, water in a proportion of 2.5 to 5.0 parts by weight toeach 100 parts by weight of said polyol.
 7. A process according to claim6 wherein the alkylene oxide addition-polymerized for the preparation ofsaid polyether polyol is propylene and ethylene oxides, with exthyleneoxide accounting for 5% to 25% in all and terminal ethylene oxideaccounting for 5 to 20%, both based on the polyol.
 8. A flexibleurethane foam produced by reacting a polyol comprising the polyetherpolyol obtained by addition polymerization of an ethylene oxide to anN-aminoethylpiperazineethylene oxide adduct as an initiator, saidpolyether polyol having a molecular weight of about 2000 to 7000 with anorganic polyisocyanate in the presence of a surfactant and a blowingagent.